In this study, we have prepared a series of poly(3,4-ethylenedioxythiophene) (PEDOT) with various molecular weight by using an inhibitor, imidazole (Im). The X-ray diffraction (XRD) results show that the PEDOT with larger molecular weight enhances the polymer chain ordering and stacking which leads to higher conductivity. With increasing the amount of Im, the conductivity of PEDOT can be increased from 4.01 S cm(-1) (Im = 0.0 M) to 153.6S cm(-1) (Im = 1.8 M). Comparisons of the cyclic voltammetry (CV), it enables correlation between the conductivity and specific capacitance, which is important for understanding the electrochemical capacitive behavior of conjugated polymer for pseudo-capacitor application. The PEDOT prepared with 1.8M Im shows a specific capacitance of 124 F g(-1), which is 2.2 times larger than the one without Im (57 F g(-1)). (C) 2011 Elsevier Ltd. All rights reserved.